Electron Probe Micro-Analysis

Massachusetts Institute of Technology | Earth, Atomospheric & Planetary Sciences (EAPS) | EAPS Research Facilities
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MIT Electron Microprobe Facility

Department of Earth, Atmospheric & Planetary Sciencessmall logo
Building & Room: 54-1221; 54-1214
Cambridge, MA 02139
Phone: (617) 253-9678, or (617) 253-9677
Fax: (617) 253-7102
e-mail: e-probe-www@mit.edu

Courses and training

X-ray Spectrometry and Imaging with the JEOL JXA-8200 Superprobe: Theory and Practice

This is a "hands-on" course open only to JEOL service engineers. However, everyone is welcome to browse through the presentation.

Course outline

  • Introduction
    • Uses of the EPMA
  • Electron optics
    • Electron emitting source
    • Electron probe parameters
    • Filament saturation
    • Electron gun brightness
    • Electron probe diameter
    • Objective lens apertures
    • Comparison of electron emitting sources
    • Electron lens aberrations
    • Working distance and depth of focus
    • Column modes
  • Spatial resolution
    • Electron interaction volume and depth (range)
    • Signal types (electron, x-ray, and light)
    • Production volume for different signals
  • Electron-specimen interactions
    • Elastic and inelastic scattering
    • Backscattered electron (BSE) generation
    • Electron backscatter coefficient
    • Backscattered electron detector
    • Compositional and topographic imaging with the BSE detector
    • Secondary electron (SE) generation
    • Everhart-Thornley detector
    • BSE and SE detection with the Everhart-Thornley detector
    • Cathodoluminescence (CL)
    • CL spectrometer: the xCLent system
    • CL spectrometry and hyperspectral imaging
    • CL image display modes
  • X-ray generation
    • Electromagnetic spectrum
    • Energy-wavelength relation
    • Characteristic x-ray generation
    • Critical excitation energy and overvoltage
    • Kα, Kβ, Lα, Lβ, Mα and Mβ x-rays
    • X-ray production depth (Castaing's formula)
    • Electron range versus x-ray range
    • Continuum x-ray generation
    • Typical x-ray spectrum
    • X-ray background (Bremmstrahlung)
  • Energy Dispersive Spectrometer (EDS)
    • Lithium-drifted silicon (Si-Li) detector
    • Spectral resolution (FWHM)
  • Wavelength Dispersive Spectrometer (WDS)
    • Focusing geometry (Rowland circle)
    • Bragg's law of diffraction
    • Diffracting crystals and layered structures (LIF, PET, TAP, LDE, etc.)
    • WDS operation: detecting a specific wavelength
    • L-value
    • Limits of spectrometer movement
    • Diffraction angle
    • Order of diffraction (1st, 2nd, etc.)
    • Curved diffracting crystals and x-ray focusing ellipsoid
    • Spectral resolution of WDS vs. EDS
    • Spectrometers with 140 mm and 100 mm focusing circle
    • Proportional counter
    • Counter window
    • Counter gas efficiency and absorption edges
    • Single channel analyzer (SCA) and pulse height analysis (PHA)
    • Escape peaks in SCA scan
    • Standard pulse height voltages and SCA configurations
    • Detector slit openings and mylar film covered slits
    • Standard crystal, counter and slit combinations
  • Electron probe microanalysis with WDS
    • Analytical procedure
    • Sample preparation and carbon coating
    • Setting up the electron microprobe
    • Qualitative analysis with BSE and EDS
    • Qualitative and semi-quantitative analysis with WDS
    • Standard x-ray intensity measurement (calibration)
    • X-ray intensity measurement: peak minus background
    • Peak overlap and resolution
    • Minimizing overlap and overlap correction
  • Quantitative analysis and matrix corrections
    • Quantitative analysis equation
    • ZAF matrix corrections
    • X-ray absorption and mass absorption coefficient
    • Depth-distribution of x-rays: the φ(ρz) function
    • φ(ρz) corrections
    • Fluorescence
    • Matrix correction flowchart
  • Compositional imaging (x-ray elemental mapping) with WDS
    • Beam-raster mode
    • Stage-raster mode
    • Background in x-ray image
    • Defocusing in beam-raster mode
    • Image quality: resolution and signal
  • Simultaneous BSE, CL, and x-ray (with WDS and EDS) mapping
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